My prior U.S. Pat. Nos. 4,496,464 and 4,966,698 disclose a filter system that has a filter media comprising particles of filter material contained within a vessel. Liquid flows through the filter media of the vessel, removing unwanted contaminants from the flowing liquid. The present invention is an improvement over the filter apparatus set forth in my previous U.S. Patents and the prior art cited therein, and to which reference is made for further background of this invention as well as mentioning the prior art.
The cited media of this invention includes pecan hulls, or a mixture of pecan hulls, walnut hulls, apricot pits, and many other useful media substances including sand as well as natural and synthetic media substances of various composition. The present invention sets forth a new filter system that utilizes these and other various filter media, wherein the filter media is scrubbed and cleaned externally of the main filtering vessel, thereby cleaning the media from time to time by removing a small portion of the media from the large portion of the media that remains within the vessel, and scrubbing the removed media clean, thereby rejuvenating it for reuse.
One of the major problems found in many of the filter systems of the above type that are in use today is the inability to maintain a uniform cross-sectional area of the media bed. The actual throughput area of a filter system has been found to be a function of the cross-sectional area that can be cleaned rather than the actual area of the filter vessel or filter bed. For example, in an original filter bed that used 78.5 square feet of area, the usable cross-section of the filter bed was found to be less than 50 square feet (8 foot diameter). This disparity between the theoretical and actual areas is directly related to the difficulty in maintaining turbulent flow adjacent to the vessel wall during backwash.
Applicant has found that when an area of the filter cannot be penetrated by the backwash flow, this area no longer functions satisfactorily for filtration and cannot be recovered by prolonged ineffectual backwash, and therefore it no longer functions as part of the filtering media.
Another problem with some above prior art filter arrangements lay in its operation as well as in its design. Starting and stopping flow through the filter causes the media to cyclicly decompress and then to recompress. This cyclic action of the media allows trapped particles within the filter media to be released when the flow through the filter media is resumed, thereby increasing the concentration of the contaminants contained within the filtered liquid. It has been found to be poor technique to allow shut down of the filters as a throughput control because this action is very detrimental to the efficiency of the deep bed filter. This shutdown allows bacteria to grow within the bed as well as causing the oil wetted particles to bind the media together. Hence, operating the filter at maximum throughput for a portion of the day, and off for the balance, reduces the quality of the filtered stream.
It is a common practice to attempt to alleviate some of these problems by using a surfactant to clean the filter bed, however this causes the resultant filter bed to become very slow in trapping particles following the backwash cycle. This causes the filter system to pass the particles through the filter bed for as much as 30 to 60 minutes after carrying out the backwash cycle, which further reduces the quality of the separated stream.
The present invention overcomes the foregoing drawbacks and achieves new and desirable results by the provision of an improved filter system along with a method of operation; and, further provides for such an improvement to be retrofitted to many existing prior art filter vessels to thereby advantageously allow the old system to be upgraded and unexpectedly improved, as will be better and more fully appreciated later on as this disclosure is more fully digested.
Throughout this disclosure, the term "contaminated water" and "dirty water" is intended to include any liquid having foreign particles admixed therein that must be separated from the liquid and discarded, or retained because of it value.